Internal combustion engine exhaust with thermoelectric generator



J -n10, 1967; v. D. PEPPER INTERNAL COMBUSTION ENGINE EXHAUST WITH THERMOEIJECTRIC GENERATOR Filed March 2, 1962 A///////////////////zdzzzfr (E INVENTOR.

P P p o n PM Fm the pipe contact. the. electrodes.

INTERNAL COMBUSTION ENGINE EXHAUST WITH THERMOELECTRIC: GENERATOR VernonD. Pepper, 101 Montrose Drive, Lockport, Ill. 60441 Filed Mar. 2, 1962, Ser. No. 177,046 4 Claims; (Cl. 136--208) Thisinvention relates to thermoelectric generators and IIlOl'CfiiSPGCifiCEIllY to a novel unit which is particularly adaptable for use in conjunction with the exhaust of any internal combustion engine or the like.

I It is well known that the exhausts of internal combustion engines are extremely wasteful in that there is a heat lossias well as loss of the pressure gases. The instant device has been developed to utilize not only this wasted heat but also the efiect of the movement of the exhaust ing a plurality of thermoelectric cells which have a hot junction with the exhaust pipe and which have a cold junction with cooling vanes or fins which are enclosed within a shroud connected to a venturi disposed in axial alignment with the discharge end of the exhaust pipe whereby the flow of the gases through the exhaust pipe and outthrough the venturi induces a flow of cooling air through. a shroud over the cooling fins in order to provide a pronounced temperature gradient between the hot and coldendsjof the electrical energy generating cells to improvethe flow of current therethrough.

These and other objects and advantages inherent in and encompassed by the invention will become more readily apparentfrom the specification and the drawings, wherein:

FIGUREl is a cross-sectional view through the exhaust pipe and the novel thermoelectric generating unit.

Description of the invention Describing the invention in detail, there is shown an exhaust pipe 2 of an internal combustion engine which is of cyl indrical form and which is preferably made of metal such assteel or the like. The exhaust pipe is surrounded by the novel thermoelectric generator generally designated 3 which includes. an annular generator body 4 formed of any suitable dielectric material such as asbestos cement board, said body 4 carrying a plurality of radially disposed j thermoelectric cells 5 which is supported within the openings 6 in the generator shell4. It will be appreciated that when two dissimilar metals are connected to each other at .two points of junction to form an electrical circuit and the two junctions are maintained at diflerent temperatures, then, depending upon the thermoelectric properties oftwo materials, current will flow in the electrical circuit. Such thermoelectric generator elements of both P type and .N. type maybe made of lead telluride and are now commercially available, or other improved elements may be utilized.

In the.instant. embodiment the cells 5 are connected at their .inner ends to hot junction electrodes 7 by pressure contacts of the order of about 100 p.s.i.. The electrodes are in contact with the surface 8 of the exhaust pipe wall 9 through an insulating porcelain cement. Actually the hot junctions may be accomplished by having an anodized aluminum surface on an aluminum sleeve surrounding The outer ends of the cells 5.13.1'6 connected by a tin-bismuth solder to cold hitedi? States Patent 0 "ice junction electrodes 10 to cooling vanes or fins 11 of any suitable material having a high thermal coefiicient such as aluminum or copper or the like. These fins or vanes 11 are radially arranged about the axis of the generator body and are preferably rectangular thin metallic members or plates which extend flatwise axially of the exhaust pipe. It will be readily understood that the elements or the cells 5 may be suitably connected to each other either in series or in parallel depending on the requirements whether a high voltage, low amperage or a low voltage high amperage electrical energy is required.

The generator is suitably secured to the exhaust pipe and in the vertical disposition such as on the exhaust of a tractor, as herein shown, the generator body may be sustained by a clamp 15 which may be clamped to the exhaust pipe wall 9. The inner ends 16 of a plurality of radial arms or bolts 17 may be supported on the hose clamp 15 between the same and the lower edge of the generator body.

The arms 17 may extend radially from the pipe 2 and at their outer ends may pass through openings 19 in the cylindrical shroud portion 20 of the housing generally designated 21.

The outer ends of the arms 17 may be threaded as at 22 and may be provided with inner and outer nuts 23 and 24 embracing opposite sides of the cylindrical portion 20 in the area adjacent to the opening 19 for securing the housing to the respective arm. Since the arms 17 are radially arranged it will be realized that collectively these arms cooperate to rigidly secure the shroud portion 20 and thus the housing 9 to the exhaust pipe.

The lower or one end of the shroud 20 provides an inlet opening as at 25 through which coolant air is drawn from the atmosphere across the cooling fins 11 as the air moves upwardly or toward the venturi portion 26 of the housing. The venturi portion comprises an inner frusto conical part 27 which merges with the adjacent edge of the shroud portion 20 and converges at a distance of 1 to 2% inches from the outlet end 29 of the exhaust pipe to a narrow throat section 30 whereat the outer frusto-conical section 31 is connected to the inner cone and said outer cone 31 flaring outwardly. It will be realized that additional supports 32 may be provided about the periphery of the pipe through the medium of the arms 33 which suitably abut as at 34 against the pipe and at their outer ends are provided with the nuts 35 and 36 which respectively engage the inner and outer sides of the Wall portion 37 of the venturi cone section 27, said nuts 35 and 36 being threaded on the outer threaded end 38 of the respective arms 33 and collectively engaging the respective wall portion 37 and securing the outer duct with respect to the pipe 2.

It will be readily realized that as the exhaust gases are being discharged in the direction shown by the arrows at 40-40 through the constricted portion 30 of the venturi there is a pressure differential developed between this area and the area designated by the reference numeral 41 which is the area within the shroud 20 and thus because of this pressure differential there is induced a flow of air through the inlet opening 20 of the housing.

It will be apreciated that in lieu of the tin-bismuth connections at the cold ends of the electrodes or cells that a simple spring-loaded pressure assembly may be used and this has the advantage of accommodating inward and outward movement of the respective electrodes as the same heat and expand and cool and contract and, therefore, it will prevent melting or destruction of the connections while accommodating the thermal action of the respective elements. In actual tests, a temperature in the vicinity of 1100 F. at the hot junction and approximately F. at the cold junction has been developed. In the actual construction the thermo-electric generator was built to operate on the exhaust pipe of an agricultural tractor. The generator contained 10 N-type and 10 P-type lead telluride thermo-elements held in an annular arrangement in the body. Fresh air cooling was provided by the venturi action of the exhaust stream which drew cooling air over fins attached to the cold junctions. The design butput was 5.2 watts or 4.3 amps. at 1.2 volts with a temperature diflerence of 1000 F. across the thermal elements. The performance of the generator was observed during actual operation and results compared with the expected performance. Two different engines were used, one was the six-cylinder 50 horsepower gasoline stationary power unit and the other was a four-cylinder 38 horsepower gasoline tractor engine. In the actual construction, a 6- inch length of 2-inch exhaust pipe was obtained. The center 3 inches of its outside surface was prepared for application of the AL-Pl cement by polishing the surface .to vbared metal and roughening it with the core file. The

ceramic cement AL-Pl was brushed on to a thickness of about 0.003 to 0.005 inch. The pipe was then placed in the oven to dry one hour at 200 F. and one hour at 600 F. with a maximum temperature increase of 200 F.

' per hour between the two drying temperatures. The generator body was made up of several donut-shaped rings of 2% inches inside diameter and 3 inches outside diameter, and were cut from /2 inch asbestos cement board. Two of these rings were each drilled with ten A1 inch diameter holes extending radially through the rings to receive the thermo-elements. Two drilled rings were located alternately between the other three rings which served as spacers and to hold the cold junction electrodes. The hot junction electrodes were made from iron straps 1%. inches long by /2 inch wide by A inch thick and were cold formed to fit the pipe contour. The thermo-elements were placed to allow the elements to move in and out as the thermal stress changed. The cold junction electrodes were constructed of 0.018 inch thick spring brass, the shape of the electrodes were such that they provided as much area as possible in which to mount fins but prevented contact between adjacent electrodes.

In the preferred embodiment the electrodes flow in the circuit was through the N-type element from hot to cold, across the cold junction electrode, through the adjacent P-type element from cold to hot and across the bottom across the hot junction electrode through the next N-type element in the row. The two rows of elements were con nected in series by cutting two cold junction electrodes and connecting the N-type and P-type elements of the cut electrodes together by bridging across the fins or vanes. Lead wires were soldered to the fins of the other half of the separate electrodes as terminals for attaching to external load. The cooling fins of 1 /2 inches long by 1 inch wide by 0.022-inch thick copper were soldered to the electrodes with a solder-flux while the electrodes were fastened loosely over the thermo-elements. The heat applied to solder the bins also joined the thermo-elements and electrodes by melting the solder at the junctions. Sixty fins were soldered to the cold junction electrodes, even though it was determined that 43 would be sufficient. This was done to improve the efiiciency of the cooling method possibly to the point that natural air cooling would be suflicient. The electrodes were then pressed down on the thermo-elements by tightening fastening screws. This provided the compressive loading required by the hot junctions.

The generator hood as shown is formed from a five quart tin cylinder which was 6 /2 inches in diameter by 8 inches long. The venturi was formed by slitting at 2 inch intervals one-half the length of the cylinder and overlapping the strips one inch, which resulted in a diameter of 1% inches at the throat. A 5%. inch funnel was cut off at the point where the diameter was 3% inches and 10 the small diameter of the funnel was placed inside the small diameter of the cylinder so that the two edges just overlapped. The two edges were joined by crimping and soldering. The hood or shroud was held to the exhaust pipe by the wire rings which were connected to radial Wire arms as described.

Having thus described the preferred form of the invention, it will be understood that various other embodiments will become readily available to those skilled in the art within the scope of the appended claims.

I claim:

1. The combination of an internal combustion engine having a hot gas exhaust duct with an outlet end, a thermoelectric generator comprising a body surrounding the duct defining a space therebetween, thermal electrical energy generating elements mounted on said body and having one of their ends in electrically insulated thermal contact with said duct, heat dissipating means connected to the other ends of said elements, shroud means surrounding the outlet end of said duct, said shroud means having a frusto-conical section extending from an area before said outlet end of the exhaust duct and terminating beyond the end of the exhaust duct, and a frusto-conical section extending from said first-mentioned frusto-conical section and inverted with respect thereto and defining a venturi therewith at an area spaced with respect to the discharge end of the exhaust duct whereby the flow of gases through the exhaust duct and out through the venturi induces a flow of cooling air in the space between said duct and body about said heat dissipating means to provide a substantial temperature difference between opposite ends of said elements.

2. The invention according to claim 1 wherein said heat dissipating means comprises fins.

3. The invention according to claim 1 and said venturi defining a throat spaced from one inch to about two and one quarter inches from the outlet end of the duct.

4. The invention according to claim 1 wherein said generator comprises N-type and P-type lead telluride elements.

References Cited by the Examiner UNITED STATES PATENTS 472,261 4/1892 Gulcher 1364 2,391,994 1/1946 McCollum 1364.11

FOREIGN PATENTS 353,252 4/1905 France.

WINSTON A. DOUGLAS, Primary Examiner.

JOHN H. MACK, Examiner.

I, ljA RNEY, A. B CURTIS, Assistant Examiners, 

1. THE COMBINATION IF AN INTERNAL COMBUSTION ENGINE HAVING A HOT GAS EXHAUST DUCT WITH AN OUTLET END, A THERMOELECTRIC GENERATOR COMPRISING A BODY SURROUNDING THE DUCT DEFINING A SPACE THEREBETWEEN, THERMAL ELECTRICAL ENERGY GENERATING ELEMENTS MOUNTED ON SAID BODY AND HAVING ONE OF THEIR ENDS IN ELECTRICALLY INSULATED THERMAL CONTACT WITH SAID DUCT, HEAT DISSIPATING MEANS CONNECTED TO THE OTHER ENDS OF SAID ELEMENTS, SHROUD MEANS SURROUNDING THE OUTLET END OF SAID DUCT, SAID SHROUD MEANS HAVING A FRUSTO-CONICAL SECTION EXTENDING FROM AN AREA BEFORE SAID OUTLET END OF THE EXHAUST DUCT AND TERMINATING BEYOND THE END OF THE EXHAUST DUCT, AND A FRUSTO-CONICAL SECTION EXTENDING FROM SAID FIRST-MENTIONED FRUSTO-CONICAL SECTION AND INVERTED WITH RESPECT THERETO AND DEFINING A VENTURI THEREWITH AT AN AREA SPACED WITH RESPECT TO THE DISCHARGED END OF THE EXHAUST DUCT WHEREBY THE FLOW OF GASES THROUGH THE EXHAUST DUCT AND OUT THROUGH THE VEN- 